Geologists have long known about the strong, round sand buried beneath the bluffs near the Mississippi River. For decades, companies have mined it for window glass and water filtration products.

But the practice has drawn widespread condemnation among environmentalists and others since energy companies discovered it helps extract oil and natural gas from the ground.

Silica sandAP Photo/The Winona Daily News, Andrew Link

The sand is used in a natural gas extraction process called hydraulic fracturing, or fracking. When the sand is forced into underground rock formations it breaks up the stone, releasing large amounts of natural gas. The hard Minnesota sand is perfect for fracking, because it can withstand the intense pressure needed to break rock.

Silica sand mining is a divisive topic in southeastern Minnesota. Local officials have held town hall meetings with residents, met with environmentalists and industry leaders, and passed moratoriums on mining so they can study the practice that has already swept parts of Wisconsin.

Nine local moratoriums in Minnesota have given rise to a public movement.

"We heard about frac sand coming to Winona about six months ago," Wilson said. "[We] got a sense for what the sand is being used for, and then ...attended a lot of meetings, wrote a lot of letters, talked to council members."

Area residents also started to hold rallies against silica sand mining, an industry that has roughly doubled in size since 2008.

Wilson helped organize a recent rally outside Winona City Hall, where a couple dozen people formed a long line on the sidewalk, and held colorful signs that read "How did this happen?" and "Don't fracture Winona."

Winona rallyMPR Photo/Elizabeth Baier

"If we believe that [the sand] is being used for something bad and immoral, then we have a right to talk about that; we have a right to do something about it," Wilson said.

Winona County has the shortest of all the moratoriums that have passed in southeastern Minnesota. It expires May 1. County officials expect at least eight permit applications for new mines by mid-May. The proposed sites are scattered throughout the county and represent less than 1 percent of its land.

"If a town is going to change its character, there needs to be some warning," Byman said. "And people need to have input and not be caught unaware by this."

Byman, a history professor at the University of Winona, said a silica sand processing facility near the river is already changing the feel of downtown.

"The town is already filling up with dust and sand and trucks," she said. "This isn't the Winona that we fell in love with and I think everybody just spontaneously has just become very alarmed in a very short period of time."

Andy PuetzMPR Photo/Elizabeth Baier

Winona County Planning and Environmental Services Director Jason Gilman has heard all sorts of perspectives from local residents in the last six months.

"We're seeing this enormous range of comment," he said.

But Gilman knows county officials need to decide how best to regulate the new mining projects that may come here.

County officials voted last year to make mining companies pay for road damages. The county also will require mining companies to submit environmental, geological, road and traffic impact studies for proposed mines. The companies also will have to submit a plan to reclaim the mines after mining operations are complete, Gilman said.

A big question for Winona County and other communities where silica sand is present is how far the mining operations will go.

"We get asked that question all the time. 'What's the end game?' or 'How big is this going to get?' " Gilman said. "Of course, we don't really know that but ... From what I've been hearing and the data I've been looking at, this is going to get pretty big.

The moratorium may have put a temporary block on new sand mining in Winona County. But the sand at a processing plant in downtown Winona is coming from across the river in Wisconsin.

Near the corner of Harriet and Second streets in downtown Winona, trucks haul load after load of silica sand from a giant stockpile onto rail carts. Officials with Modern Transport, the company that runs the transportation facility, declined to comment.

But nearby businesses like Chrysler Winona have noticed more activity in the area.

"People have come by and said they can't tell the color of the vehicles," said Andy Puetz, general manager at the dealership. "If people can't tell even the color of it, you can really tell there's been sediment in the air and some fallout from operations here in the area."

Puetz said the local economy could benefit from new mining operations. But he's had to hire additional workers and is spending $2,000 a month just to keep the 130 cars on his lot clean.

Winona city officials are considering a separate moratorium vote on March 19 which could halt mining expansion within the city limits for at least a year.